I wouldn't choose to sit right at the back – all the things mentioned above are likely to be true: it can be noisy, especially if there is a galley at the back, there will a lot of traffic up and down the aisle and people standing around, the lavatories can be smelly (although one hopes not, certainly on a "good" airline), and it is often not as dark as other areas when the cabin is lit for "night-time". And yes, it will take a long time to disembark at the end of the flight.